Wireless power coupling allows electrical energy to be transferred from a power supply to an electric load without connecting wires. A power supply is wired to a primary coil and an oscillating electric potential is applied across the primary coil which induces an oscillating magnetic field therearound. The oscillating magnetic field may induce an oscillating electrical current in a secondary coil, placed close to the primary coil. In this way, electrical energy may be transmitted from the primary coil to the secondary coil by electromagnetic induction without the two coils being conductively connected. When electrical energy is transferred inductively from a primary coil to a secondary coil, the pair are said to be inductively coupled. An electric load wired in series with such a secondary coil may draw energy from the power source when the secondary coil is inductively coupled to the primary coil.
Leaks may arise if a foreign object, for example one which is metallic and/or magnetic, is located between the primary and secondary coils during charging. Besides inefficiencies which may arise owing to lost energy, the presence of a foreign object within an inductive couple may result in parasitic heating, thereby posing a hazard.